This invention relates, in general, to bleaching and laundering compositions and their application to laundering operations. More specifically, this invention relates to bleaching and laundering compositions containing a peroxygen compound, an organic activator for said peroxygen compound comprising phthalic anhydride and a defined phosphonate compound.
Bleaching compositions which release active oxygen in the laundry solution are extensively described in the prior art commonly used in domestic laundering operations. In general, such bleaching compositions contain peroxygen compounds, such as, perborates, percarbonates, perphosphates and the like which promote the bleaching activity by forming hydrogen peroxide in aqueous solution. A major drawback attendant to the use of such peroxygen compounds is that they are not optimally effective at the relatively low washing temperatures employed in most household washing machines in the United States, i.e., temperatures in the range of 80.degree. to 130.degree. F. By way of comparison, European wash temperatures are generally substantially higher extending over a range, typically, from 90.degree. to 200.degree. F. However, even in Europe and those other countries which generally presently employ near boiling washing temperatures, there is a move to lower temperature laundering.
In an effort to enhance the bleaching activity of peroxygen bleaches, the prior art has employed materials called activators in combination with the peroxygen compounds. It is generally believed that the interaction of the peroxygen compound and the activator results in the formation of peroxyacid which is the active species for bleaching. Numerous compounds have been proposed in the art as activators for peroxygen bleaches among which are included carboxylic acid anhydrides such as those disclosed in U.S. Pat. Nos. 3,298,775; 3,338,839 and 3,532,634; carboxylic esters such as disclosed in U.S. Pat. No. 2,995,905; N-acyl compounds such as those described in U.S. Pat. Nos. 3,912,648 and 3,919,102; cyanoamines such as described in U.S. Pat. No. 4,199,466; and acyl sulfonamides such as disclosed in U.S. Pat. No. 3,245,913.
The use of chelating agents in bleaching compositions is described in the patent literature. U.S. Pat. No. 3,243,378 to Stoltz discloses a bleaching composition containing a hypochlorite or peroxide type bleaching material and a chelating agent to sequester metal cations. U.S. Pat. No. 4,225,452 to Leigh discloses the combination of specified classes of chelating agents (among which are phosphonate compounds) with peroxygen compounds and an organic activator for the purpose of suppressing the decomposition of the peroxygen compound in the bleach composition; specifically, inhibiting the unwanted reaction of the peroxygen compound with a peroxyacid to form the corresponding carboxylic acid, oxygen and water. The patentee, however, states that the efficacy of such chelating agents is restricted to certain peroxygen compound/activator systems. Specifically, at column 2, beginning at line 63, the patentee states that certain activators, such as phthalic anhydride, "which form with the percompound in solution a peracid having a double bond between the carbon atoms in the .alpha.,.alpha.' position to the carbonyl groups of the corresponding anhydride ring", are excluded from use in the bleaching compositions described in the patent because of their instability.
Phthalic anhydride has, however, been disclosed in the art as an activator for peroxygen compounds, although it apparently was ineffective for such purpose. Specifically, U.S. Pat. No. 3,338,839 is directed to a bleaching composition containing as an activator a mixed carboxylic acid anhydride. In Example I of the patent, phthalic anhydride was used as an activator in a comparative test run, the results of which illustrated the ineffectiveness of phthalic anhydride as an activator when used alone, as compared to the mixture of activators used in the bleaching composition of the patent.